Biofertilization with photosynthetic bacteria as a new strategy for mitigating photosynthetic acclimation to elevated CO2 on cherry tomato

Abstract

The stimulated effects of elevated CO2 concentration decline over time in many C3 plants. However, the phenomenon is a rare occurrence on plants hosting some symbiosis bacteria. The photosynthesis acclimation associated with an extended period of high CO2 concentration was therefore studied in cherry tomato that treated with a kind of photosynthetic bacteria. Bio-fertilization with photosynthetic bacteria, which can fix nitrogen for host crops and contains a variety of growth promoting factors, can play an important role in maintaining photosynthetic activity. In this research, we conducted a CO2 elevation experiment combined different water regimes and inoculation with photosynthetic bacterium, to evaluate the improvement of photosynthesis acclimation by using photosynthesis bacteria, and to explore associated mechanisms for artificial chamber grown cherry tomatoes. As a result of these experiments, we found that elevated CO2 had a positive effect on cherry tomato photosynthetic activity and yield of all treatment. After 55 days of CO2 injection, photosynthetic acclimation was found in the plant of uninoculated photosynthetic bacteria, which were most pronounced in high water treatments. Reduced irrigation amounts decreased the magnitude of photosynthetic acclimation, but relative fruit yield gradually decreased after achieving a maximum. In contrast, the photosynthetic bacteria inoculated plants just showed a slightly down-regulation of photosynthesis under durative high CO2 condition. Because inoculation of photosynthetic bacteria increased the photosynthetic pigment content, mesophyll conductance, maximum carboxylation rate and maximum electron transport rate. Furthermore, inoculation with the photosynthetic bacteria diminished the yield penalties caused by the reduced irrigation treatment through promoting nitrogen content and relieve starch accumulation in tomato leaves compared to those of the uninoculated control. And enhanced yield of inoculated plants grown under durative high CO2 concentration were observed. The results suggest that photosynthesis bacteria application could be a potential means to further improve the CO2 stimulation effect on cherry tomato production.